Small touches to bitbase.cpp

Inspired by Lucas's code:

https://github.com/lucasart/chess/blob/master/src/kpk.cc

No functional change.
Move classify_leaf() to c'tor in bitbases

No functional change.
Don't blunder under extreme time pressure

We always attempt to keep at least this emergencyBaseTime
at clock. But if available time is very low it means that
we will force ourself to play immediately to satisfy the
emergencyBaseTime constrain and so leading to blunders.

Patch is good at short and very short TC (15secs and 5secs respectively)
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 26590 W: 5426 L: 5245 D: 15919

LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 5767 W: 1397 L: 1268 D: 3102

Instead seems has no influence at longer TC (60 secs)
LLR: -2.96 (-2.94,2.94) [0.00,6.00]
Total: 79862 W: 13623 L: 13339 D: 52900

So it is committed to have a broader testing but is
to be consider still EXPERIMENTAL and can be reverted
easily.

No functional change.
Fix operator++ definition

ENABLE_OPERATORS_ON has incorrect definitions of
post-increment and post-decrement operators.

In particularly the returned value is the variable
already incremented/decremented, while instead they
should return the variable _before_ inc/dec.

This has no real effect because are only used in loops
and where the returned value is never used, neverthless
it is wrong. The fix would be to copy the variable to a
dummy, then inc/dec the variable, then return the dummy.

So instead, rename to pre-increment that can be implemented
without the dummy, actually the current implementation
it is already the correct pre-increment, with the only change
to return a reference (an l-value) and not a copy, so
to properly mimic the pre-increment on native integers.

Spotted by Kojirion.

No functional change.
Use pre-increment also for native types

Now that we use pre-increment on enums, it
make sense, for code style uniformity, to
swith to pre-increment also for native types,
although there is no speed difference.

No functional change.
Nicer operator declerations

No functional change.
Code style at passed pawn eval

No functional change.
Rewrite unstoppable pawns evaluation

Instead of current code, give a bonus according to the frontmost
square among candidate + passed pawns.

This is a big simplification that removes a lot of accurate code
substituting it with a statistically based one using the common
'bonus' scheme, leaving to the search to sort out the details.

Results are equivalent but code is much less and, as an added bonus,
we now store candidates bitboard in pawns hash and allow this
info to be used in evaluation. This paves the way to possible
candidate pawns evaluations together with all the other pieces,
as we do for passed.

Patch passed short TC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 16927 W: 3462 L: 3308 D: 10157

Then failed (quite quickly) at long TC
LLR: -2.95 (-2.94,2.94) [0.00,6.00]
Total: 8451 W: 1386 L: 1448 D: 5617

But when ran with a conclusive 40K fixed games at 60 secs it proved
almost equivalent to original one.

ELO: 1.08 +-2.0 (95%) LOS: 85.8%
Total: 40000 W: 6739 L: 6615 D: 26646

bench: 3884003
Fix time parameters for blitz games

The ideal setting for super-blitz might be something like:

    "Emergency Base Time" = 50
    "Emergency Move Time" = 5

This would give a total emergency time buffer of:

    50 + 40 * 5 = 250 ms

This setup replaces the previous half cooked hack
"Don't blunder under extreme time pressure".

Test results are very good at super blitz, but keep good even
at 60 secs.

At 5+0.05
ELO: 24.30 +-2.4 (95%) LOS: 100.0%
Total: 37802 W: 10060 L: 7420 D: 20322

At 15+0.05
ELO: 13.41 +-2.9 (95%) LOS: 100.0%
Total: 22271 W: 4853 L: 3994 D: 13424

At 60+0.05
ELO: 5.30 +-3.2 (95%) LOS: 99.9%
Total: 16000 W: 2897 L: 2653 D: 10450

No functional change.
Fix a silly unstoppable eval bug

The logic is broken for black side because we get more bonus
for pawn in 7th rank than for pawn in 2nd rank!

Spotted by Reuven Peleg

bench:3884409
Increase Emergency Move Time to 10

Goes in the direction of avoiding time losses and seems
equivalent after almost 40K games at super fast TC of 10+0.05

ELO: 2.41 +-2.3 (95%) LOS: 98.1%
Total: 37222 W: 7843 L: 7585 D: 21794

No functional change.
Merge remote-tracking branch 'upstream/master'
Change some iterators from postfix to prefix to stay in line with Stockfish.